[W126 Coupe] Slightly High Idle - Possible Causes
Larry Martin
lmartin at austin.rr.com
Tue Jun 26 09:53:18 EDT 2007
John,
Idea #1:
It sounds like you are on the right track. I found a similar problem,
and while all the main idle components (cold start valve, idle control
valve, idle control unit) were all working properly, there was a slight
leak (vacuum) near the idle control valve causing a higher idle. Test is
to move the (vacuum) lines in and around the Idle Control Valve to see
if you can affect the idle speed. If you still suspect the Idle Control
Unit...you know about removing the idle control unit connecter (Idle
Control Unit is near center of windshield on Firewall) to see if the
idle speed 'jumps' up. In my case...I used black "make a gasket" to seal
the slight leak...and it worked perfectly thereafter.
Idea #2:
If this fails, you may find that the levers you THINK are working ok
below the Fuel Injection Distributor are working...but shellac can cause
them to slightly stick. A quick test is to spray good quality carb
cleaner spray (open the air metering plate with your finger) and spray
the cleaner toward the rear of the air handling unit - toward the Fuel
Distributor. Restart the car (yes...it will crank a maybe up to 10 times
before starting) and see if the idle changes. If it does, you will have
to remove the Fuel Distributor and clean the levers you find there until
they move very easily.
Idea #3:
Also...when the fuel distributor is removed...test the plunger (in the
center of the bottom of the Fuel Distributor unit) to see if it is
"hard" to move...if it is...that too can cause the idle to be high since
it would keep the levers from working completely to the end of travel.
Incidentally...the idle speed should not come back to minimum speed in a
minute...that is pretty fast...more normal is to return to minimum idle
after a handful of minutes...even in a warm climate, after a cold start.
Good Luck!
Larry Martin
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Today's Topics:
1. Slightly high Idle- What next? (JohnJayKimrey1 at aol.com)
2. Edmund (Dineshh)
3. Re: Slightly high Idle- What next? (Neil)
4. Re: Slightly high Idle- What next? (Tim Graney)
5. Re: Repair Manuals (RSLeeH2O at aol.com)
6. Re: Repair Manuals (Tim Graney)
----------------------------------------------------------------------
Message: 1
Date: Mon, 25 Jun 2007 16:56:13 EDT
From: JohnJayKimrey1 at aol.com
Subject: [W126 Coupe] Slightly high Idle- What next?
To: mbcoupes at mbcoupes.com
Message-ID: <c4d.18070bd6.33b185ed at aol.com>
Content-Type: text/plain; charset="us-ascii"
Hello everyone:
I know most of you have heard enough on this subject but I am not sure
what
to do next and any and all advice and information I can get is
appreciated .I
have an idle of 850 rpm in park or drive with or without a/c. It is
smooth
and doesn't change after initial warm up. I have checked for vacuum
leaks and
found none. Air metering plate moves freely and closes without a
problem. OVP
relay is new(previously sticking and ABS light was on and rpm 1100).No
binding of throttle linkage and throttle valve closes freely. Throttle
valve
switch checked good for both open and closed position with ohm meter,
Idle control
valve(ICV) appears to be operating but cannot tell if it is closing
completely. When disconnected idle goes to about 1800 rpm and connected
to 850 rpm.
Resistance is 4.5 ohms and voltage across connector is about 5
volts+-.2 volts
when connected and at idle.The valve is moving freely inside as I
removed
and checked it. Thermo time switch and cold start injector are working
as idle
dropped to 850 from 1100 after about 30 seconds of start up but not to
550-650.Is there anything I may have missed and does my problem now
direct me
toward buying an expensive idle control valve and or idle control unit.
I don't
have access to either units to swap and no MB mechanic in town. Any
advice is
appreciated. Oh yes, my vehicle is a 89 SEC with 80K miles and records
show
scheduled servicing. I bought the car in May 2007. It had the high idle
problem when purchased.
Regards,
John K.
************************************** See what's free at
http://www.aol.com.
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Message: 2
Date: Mon, 25 Jun 2007 18:05:10 -0500
From: "Dineshh" <dineshh at earthlink.net>
Subject: [W126 Coupe] Edmund
To: "MBCOUPES" <MBCOUPES at MBCOUPES.COM>
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Message: 3
Date: Mon, 25 Jun 2007 14:27:54 -0700 (PDT)
From: Neil <mylimortgage at yahoo.com>
Subject: Re: [W126 Coupe] Slightly high Idle- What next?
To: Mercedes Coupes Mailing Lists <mbcoupes at mbcoupes.com>
Message-ID: <506892.72512.qm at web58910.mail.re1.yahoo.com>
Content-Type: text/plain; charset="iso-8859-1"
check these guys out if you need the ICU or ICV. the have some great
pirces and warranty thier parts.
http://www.programainc.com/doc/M-Benz.html
Neil
'83 500 SEC
JohnJayKimrey1 at aol.com wrote:
Hello everyone:
I know most of you have heard enough on this subject but I am not sure
what to do next and any and all advice and information I can get is
appreciated .I have an idle of 850 rpm in park or drive with or without
a/c. It is smooth and doesn't change after initial warm up. I have
checked for vacuum leaks and found none. Air metering plate moves freely
and closes without a problem. OVP relay is new(previously sticking and
ABS light was on and rpm 1100).No binding of throttle linkage and
throttle valve closes freely. Throttle valve switch checked good for
both open and closed position with ohm meter, Idle control valve(ICV)
appears to be operating but cannot tell if it is closing completely.
When disconnected idle goes to about 1800 rpm and connected to 850 rpm.
Resistance is 4.5 ohms and voltage across connector is about 5 volts+-.2
volts when connected and at idle.The valve is moving freely inside as I
removed and checked it. Thermo time switch and cold start injector are
working as idle dropped to 850 from 1100 after about 30 seconds of
start up but not to 550-650.Is there anything I may have missed and does
my problem now direct me toward buying an expensive idle control valve
and or idle control unit. I don't have access to either units to swap
and no MB mechanic in town. Any advice is appreciated. Oh yes, my
vehicle is a 89 SEC with 80K miles and records show scheduled servicing.
I bought the car in May 2007. It had the high idle problem when
purchased.
Regards,
John K.
---------------------------------
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Postings remain property of MB Coupes, L.L.C.
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Message: 4
Date: Mon, 25 Jun 2007 14:34:31 -0700
From: "Tim Graney" <graneyt at americancylinderhead.com>
Subject: Re: [W126 Coupe] Slightly high Idle- What next?
To: "'Mercedes Coupes Mailing Lists'" <mbcoupes at mbcoupes.com>
Message-ID: <000001c7b770$a15682d0$7901a8c0 at timpc>
Content-Type: text/plain; charset="us-ascii"
First thing to check is that the linkage has not been adjusted to raise
the idle. Disconnect the linkage right at the throttle plate and see if
the idle goes down to where it should be. If it does just lengthen the
rod to fit. Secondly, check for vacuum leaks. Put a vacuum gauge on a
manifold source. There should be three sources. One on each side of the
manifold and one in the rear of the manifold. Look for even readings of
20 bar, needle should not fluctuate at all if it does there is a leak or
leaks.
Any additional air coming into the system will increase the idle. Leaks
can be anywhere. The biggest culprit are the rubber O ring gaskets that
connect the upper and lower pieces of the intake manifold. If you have a
Mighty Vac you can check for leaks yourself. Check all the vacuum
connections for cracks and loose connections. Check the rubber
connectors on the idle control valve for tightness, they become dry and
brittle with age and loosen up creating leaks. There are a myriad of
connections behind the dashboard that control the HVAC system. Be
patient and eliminate each connection as you go along. The vacuum gauge
is your friend and they are cheap. You can tune your car with one of
these.
It sounds like your idle control valve is OK. The unit itself might be
bad, there is no way of knowing without the proper equipment to test the
unit. If you buy a new or rebuilt unit make sure you get the unit that
matches your vin# there are differences.
The CIS system is very competent but also very mechanically complicated.
When fresh the system is great but it tends to become problematic as it
gets older. A great Benz Mechanic once told me years ago that it is not
the mechanical systems that fail on Benzes it is the organic components,
i.e.. rubber connections and gaskets.
Hope this helps out
Tim Graney
1959 190sl
1965 250 se coupe
1961 300d Adenauer
1985 500 sec amg
----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of
JohnJayKimrey1 at aol.com
Sent: Monday, June 25, 2007 1:56 PM
To: mbcoupes at mbcoupes.com
Subject: [W126 Coupe] Slightly high Idle- What next?
Hello everyone:
I know most of you have heard enough on this subject but I am not sure
what to do next and any and all advice and information I can get is
appreciated .I have an idle of 850 rpm in park or drive with or without
a/c. It is smooth and doesn't change after initial warm up. I have
checked for vacuum leaks and found none. Air metering plate moves freely
and closes without a problem. OVP relay is new(previously sticking and
ABS light was on and rpm 1100).No binding of throttle linkage and
throttle valve closes freely. Throttle valve switch checked good for
both open and closed position with ohm meter, Idle control valve(ICV)
appears to be operating but cannot tell if it is closing completely.
When disconnected idle goes to about 1800 rpm and connected to 850 rpm.
Resistance is 4.5 ohms and voltage across connector is about 5 volts+-.2
volts when connected and at idle.The valve is moving freely inside as I
removed and checked it. Thermo time switch and cold start injector are
working as idle dropped to 850 from 1100 after about 30 seconds of
start up but not to 550-650.Is there anything I may have missed and does
my problem now direct me toward buying an expensive idle control valve
and or idle control unit. I don't have access to either units to swap
and no MB mechanic in town. Any advice is appreciated. Oh yes, my
vehicle is a 89 SEC with 80K miles and records show scheduled servicing.
I bought the car in May 2007. It had the high idle problem when
purchased. Regards, John K.
_____
See what's free at AOL.com
<http://www.aol.com?ncid=AOLAOF00020000000503> .
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Message: 5
Date: Mon, 25 Jun 2007 17:37:58 EDT
From: RSLeeH2O at aol.com
Subject: Re: [W126 Coupe] Repair Manuals
To: mbcoupes at mbcoupes.com
Message-ID: <c9f.10093bc3.33b18fb6 at aol.com>
Content-Type: text/plain; charset="us-ascii"
Hello,
I have a 1988 560 SEC. I have been looking for a good repair manual. I
did
buy one of the CD versions from Ebay but it requires a strange driver
that
messes with my computer. Anyone know where a hardcopy can be found?
Ron Lee
************************************** See what's free at
http://www.aol.com.
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Message: 6
Date: Mon, 25 Jun 2007 14:40:27 -0700
From: "Tim Graney" <graneyt at americancylinderhead.com>
Subject: Re: [W126 Coupe] Repair Manuals
To: "'Mercedes Coupes Mailing Lists'" <mbcoupes at mbcoupes.com>
Message-ID: <001d01c7b771$725ccba0$7901a8c0 at timpc>
Content-Type: text/plain; charset="us-ascii"
Try books4cars.com I have bought many manuals from them over the years.
They have reprint manuals for just about anything
Tim Graney
-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of RSLeeH2O at aol.com
Sent: Monday, June 25, 2007 2:38 PM
To: mbcoupes at mbcoupes.com
Subject: Re: [W126 Coupe] Repair Manuals
Hello,
I have a 1988 560 SEC. I have been looking for a good repair manual. I
did buy one of the CD versions from Ebay but it requires a strange
driver that messes with my computer. Anyone know where a hardcopy can be
found?
Ron Lee
_____
See what's free at AOL.com
<http://www.aol.com?ncid=AOLAOF00020000000503> .
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